Photovoltaic cell and manufacturing method thereof

Abstract

A photovoltaic cell includes a photoelectric conversion element (PCE) in which an i-type silicon layer formed of a microcrystalline silicon film is provided between an n-type silicon layer and a p-type silicon layer, and the n-type silicon layer or p-type silicon layer positioned on a substrate side is configured of an amorphous silicon film. The PCE is formed wherein a mixture of a silane containing gas and hydrogen gas is introduced into a chamber and a seed layer formed of a microcrystalline silicon film is formed between the n-type silicon layer or p-type silicon layer positioned on the substrate side and the i-type silicon layer. The crystallization rate of a portion in contact with the n-type silicon layer or p-type silicon layer positioned on the substrate side is lower than that of the i-type silicon layer, and the rate increases continuously, or gradually in two or more stages, toward the i-type silicon layer side, continuing to the i-type silicon layer.

1 . A photovoltaic cell having at least one or more layers of a photoelectric conversion element in which an i-type silicon layer formed of a microcrystalline silicon film is provided between an n-type silicon layer and a p-type silicon layer, the photovoltaic cell being characterized in that
 the photoelectric conversion element is such that the n-type silicon layer or p-type silicon layer positioned on a substrate side is configured of an amorphous silicon film, and   a seed layer formed of a microcrystalline silicon film is provided between the n-type silicon layer or p-type silicon layer positioned on the substrate side and the i-type silicon layer, with the crystallization rate of a portion in contact with the n-type silicon layer or p-type silicon layer positioned on the substrate side being lower than that of the i-type silicon layer, and the crystallization rate increasing continuously, or gradually in two or more stages, toward the i-type silicon layer side, continuing to the i-type silicon layer.   
     
     
         2 . The photovoltaic cell according to  claim 1 , wherein the seed layer is configured of two or more layers of microcrystalline silicon film with differing crystallization rates. 
     
     
         3 . The photovoltaic cell according to  claim 1 , wherein, when the i-type silicon layer and seed layer are each formed on the same substrate, the seed layer is formed under film forming conditions such that films of microcrystalline silicon with a crystallization rate higher than that of the i-type silicon layer can be formed. 
     
     
         4 . A method of manufacturing a photovoltaic cell having at least one or more layers of a photoelectric conversion element in which an i-type silicon layer formed of a microcrystalline silicon film is provided between an n-type silicon layer and a p-type silicon layer, and the n-type silicon layer or p-type silicon layer positioned on a substrate side is configured of an amorphous silicon film, the method being characterized in that
 the photoelectric conversion element is formed using a plasma CVD method whereby a mixture of a silane containing gas and hydrogen gas is introduced into a chamber, and   a seed layer formed of a microcrystalline silicon film is formed between the n-type silicon layer or p-type silicon layer positioned on the substrate side and the i-type silicon layer, with the crystallization rate of a portion in contact with the n-type silicon layer or p-type silicon layer positioned on the substrate side being lower than that of the i-type silicon layer, and the crystallization rate increasing continuously, or gradually in two or more stages, toward the i-type silicon layer side, continuing to the i-type silicon layer.   
     
     
         5 . The photovoltaic cell manufacturing method according to  claim 4 , wherein formation of the seed layer is started under a condition such that the concentration of silane containing gas in the mixture is lower than that when forming the i-type silicon layer, in a condition in which the pressure inside the chamber, the applied power, and the inter-electrode distance are constant, and the concentration of silane containing gas in the mixture is increased continuously, or gradually in two or more stages, eventually being increased as far as the concentration of silane containing gas when forming the i-type silicon layer. 
     
     
         6 . The photovoltaic cell according to  claim 2  wherein, when the i-type silicon layer and seed layer are each formed on the same substrate, the seed layer is formed under film forming conditions such that films of microcrystalline silicon with a crystallization rate higher than that of the i-type silicon layer can be formed.